Operating means for fluorescent lamps



Aug. 31, 1943.

J BERTRAM OPERATING MEANS FOR FLUORESCENT LAMPS Filed May '7, 1941 lfiverfitor. Johr-w Bert Far-n, by JVWTJMMZM His Attorney.

describedsomnstructedand Patented Aug. 31, 1943 UNITED STATES PATENT orrics- OPERATING MEANS FOR FLUORESCENT LAMPS John Bertram, Rugby, England, assignor to General Electric Company, a corporation of New York Application May 7, 1941, Serial No. 392,386 In Great Britain May 21, 1940 10 Claims.

This invention relates to lamp holders and to an associated electrical starting circuit for double-ended electric discharge lamps, forexample, fluorescent lamps of the type now in commercial use.

Such lamps are frequentlystartedby means of a resonant circuit which may includ a choke transformer and capacitor in series for supplying current to a pair of secondary windings connected to the heating'cathodesat each end of the lamp. This arrangement is' such that a resonant circuit isformed by the capacitor and choke transformer to provide a hi her initial current heating the cathodes rapidly so that the the lamp, the shunt path is broken causing reestablishment ofthe resonant circuit. Upon replacement of the lamp in case of'failure, it is desirableto destroy the resonant circuit to prevent the heavy'current from damaging the associated electrical apparatus or injuring a careless workman "replacing the lamp. It is further advantageous to break the resonant-circuit automaticaliy by removal of the lamp from the assoelated lamp holder rather than through the provision of a separate switching means. To this end, one of thelamp holders is provided with a switching means operable upon removal of the lsmptointerrupttheresonantcircuit. Inthis casetheswitchingmeans operatestodisconnect the condenser, from its series relationshipwith thechoketransformertherebyca'usinganinter-. ruptiontsof the resonant circuit throughthese Itis as... or the invention to Provide a holder for sn'eiectric dischargelsmp'od thetybe automaticallybyremovalofthelamp videanimprovedlampholderofthetypedewhich a switching mechanism by movement of the lamp within the Fig. 1 is a secthe-holdeptahn along the line' I'--l sign. 2- and he r in seated engagement with the contacts of the lamp holder; Fig. 2 is a side view of the holder, partly in section, showing an electric discharge lamp mounted in position; Fig. 3 is a view of the switching mechanism of the holder taken along the line 3-3 of Fig. 2; Fig. 4 is a diagrammatic showing of the resonant circuit for operating the lamp and illustrates the manner in which the switching mechanism of the lamp holder is connected into the circuit; and Fig. 5 is a perspective view of the end ferrule of the lamp.

Referring to the drawing, there is shown a tubular electric discharge lamp ill, for example, a fluorescent lamp of thetype now in commercial use, each end'ofthe lamp being provided with a fen'ule il carrying spaced contact members or prongs l2. As shown by Fig. 5, the ferrule is provided with a spacer element ii of insulating material which is disposed between the contact prongs l2 and'which is provided with an enlarged outer endor extension I4 carrying a shorting or conducting member ii for a purpose to'be described later.

The lamp holder for mounting the lamp is constructed in two parts, designated part I and part 2, which are shown individually by Figs. 3 and 1 respectively, while the assembled lamp holder is shown by Pig. 2. In the assembled position of parts I and 2 shown by Fig. 2, the parts are mounted back'to backand are separated by means'of a plate of insulating material I which spaces the parts from one another; the parts are held together with the plate 3 by any suitable fastening means such as rivets (not shown).

Turning now to a consideration of the construction of part 2 and referring particularly to -1"ig.1,thispartisformedwithabodyorhousing of insulating materialit having a chamber il provided with a slot ll extending to an outer edge of the housing and having a width smaller than the spacingof the prongs it. In chamber ii are two spaced contact members it and II, adapted to cooperatewith the contact prongs of the tubular lamp; the contact members are provided with extensions seated in the spaced channels 2| formed in the housing I andthe ends of the contact members are provided with an gularly extending terminal portions 22 which restinrecessesllformedinthebaseofthe housing. A terminal screw It is mounted in the terminal portion of each" of the contact members forwiringthelampholderto asource ofcurrent. The contact members II and 20 are formed'o'f flexible material such as spring bronze andthey are normally located in the plane of an opening 25 formed of the front edg of the lamp holder which merges with the slot ll. 'Ihismeansthatthecomactpinsofthelamp may be moved in a straight line downwardly through the slot I3 and thereafter rotated within the opening 25 to bring them into engagement with th contact members, this position being shown by Fig. 1.

Part I of the lamp holder is likewise formed with a housing of insulating material 26 which is provided with an enlarged recess 21 at one end for receiving the spaced contact members" and 29. These members are formed of flexible material, such as spring bronze, and are provided with extending portions seated within the channels 30 formed in the housing 26; they'are likewise formed with laterally extending terminal Portions 3| seated within recesses 32 in the base of the housing and cooperating with terminal screws 33 for connection with the electrical circuit. A slot 34 of a width smaller than the length of the shorting or switch member I is formed at the upper portion of .the housing 26 and. extends from the chamber 21 to the outer edg of the housing; this slot receives the outer end of the spacer member l4 formed on the end ferrule of the lamp. The spacer member I passes through this slot upon mounting the lamp in the holder and as the lamp is rotated to bring the contact prongs into engagement with the contact members l9 and 20 of the socket, the spacer I4 is likewise rotated to bring the shorting member l5 into engagement with the spaced contact members 28 and 29. This is the position shown by Fig. 3.

When the parts I and 2 are placed back to back on each side of the insulating spacer 3, the pairs of contact blades l9 and 26 and 26 and 29 are spaced from each other laterally and a restricted opening 35 is formed in the. insulating separator member 3. The upper end of the opening 35 is extended to form a slot 36 extending to the outer edges of the member so that upon insertion of'the lamp the spacer l3 will pass downwardly through the'slot 36 and rotate within the opening 35, but the opening 35 is of smaller diameter than that necessary to receive the end extension l4 of the spacer member so that this extension is maintained within the chamber 21 and cannot be: ulled transversely of the socket to bring the shorting member IS in contact with the contact members l9 and 20.

A two part lamp holder of the type described is used as one of the lamp holders to support one end of the lamp in those cases where the lamp is to be operated by means of a resonant circuit., An arrangement of this type is shown by Fig. 4. The right-hand end of the lamp is provided with a two partlamp holder of the type longer resonates.

thence across the shorting member ii to the other contact member 29 and thence through line 45 to a capacitor 46 to the other supply line 36. The condenser 46 is of such capacity as to form with th choke transformer 39 a resonant circuit so that initially a large flow of current takes place through the transformer primary. The resulting voltage of the secondary windings 40 effects a rapid heating action of the cathodes 43 at opposite ends of the lamp. This is of advantage in that it increases the speed with which the lamp starts after the operating switch has been turned on. As soon as the cathodes 43 have been heated sufliciently, an arc strikes between the cathodes thereby lighting the lamp. This are forms a shunt path across the capacitor whereby the circuit of the transformer 39 no Current now flows from the supply line 31 to the transformer 39, line 44, contact 26 to the right-hand cathode 43, thence across the arc path to the left-hand cathode, a corresponding contact member 20 of the lamp holder, a line 41 to the other supply line 38. A choke coil 46 is'inserted in the lead 41 to limit the flow of current through the lamp.

As long as the lamp is operating it provides a short circuiting path around the capacitor, hence the circuit formed by the capacitor 46 and the transformer 39 no longer resonates so that there ciated apparatus.

is again built up in the resonant circuit. During removal of' the lamp In the interruption of the high intensity current might be injurious to the associated apparatus or even to the workman replacing the lamp were it not for the fact that the I2 of the lamp. The lamp'is wired according to the circuit arrangement shown by Fig. 4.

With the lamp in mounted position, current from the supply-lines 31 and 36 flowsto a choke transformer 39 having a pair of secondary winding's 40. Each secondary winding is connected to a corresponding cathode at the end of the lamp by means of supply lines 4| and 42 connected to the contact members l6 and 26 of the lamp holder so that current is fed to the cathodes through the connector prongs l2 on the ends of the lamp. The current path through the choke transformer is from the supply line 31 through the transformer, line 44 to the contact member 26 and shorting member l5 must be rotated upon removal of the lamp to open the circuit across the contact members 26 and 29 thereby cutting out the condenser 46 and breaking down the resonant circuit through this element and the choke transformer 39. By providing the shorting member IS on the end ferrule of the lamp, it will be apparent that it is unnecessary to employ separate switching means to break the resonant circuit. .While the operating means for controlling the circuit across the contact members 26 and 29 has been shown as incorporated on th end ferrule of the lamp, it should be obvious that the specific switching arrangement shown might be replaced by onein which the contacts are opened and closed by engagement with other portions of the lamp so long as the switching arrangement is operated by rotation of the lamp within the lamp holder or upon removal of the lamp from the holder.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination with a tubular lamp provided with a ferrule having spaced contact prongs, means for connecting and starting the lamp including a socket having a two-part housing, one part of said housing being provided with a recess-in. a face thereof and extending to an outer edge of said ho ing, spaced contact blades in said recess, the other part of said housing being provided with a second recess, switch contact members'in said second recess, switch operating meanscarrled by one of the lamp ferrules, the lamp being mounted onsaid socket by straightline movement of the lamp prongs transversely to the axis of the lamp through the outer portions of said recesses and in direction of a plane through the prongs and subsequent rotation of the prongs to bring them into engagement with the spaced contact blades and simultaneously causing said switch operating means to operate said switch contact members.

2. In combination with a lamp having spaced contact prongs, a housing provided with a recess in a face and extending to an outer edge thereof, spaced contact members in said recess, said recess having a width in the outer edge smaller than the spacing of the prongs to require upon assembly movement of the lamp prongs in alignment transversely to the axis of the lamp into said recess and rotation into engagement with said spaced contact members upon seating the lamp in said socket, and separate switch means mounted on said socket and being operated upon rotation of the lamp to control the circuit to the lamp.

3. In combination with a lamp having spaced contact prongs, a housing provided with a recess in 'a face and extending to an outer edge thereof, spaced contact blades in said recess, said housing being provided with a second recess, relatively movable contact members disposed into said recess. the lamp prongs being moved in alignment transversely to the axis of the lamp into said recess and rotated into engagement with said space'd contact members upon seating the lamp in said socket, and means for operating said movable contact members in response to rotation of the lamp in said socket.

4. In combination with a double-ended discharge lamp having a cathode at each end connected'to spaced contact prongs. a socket at each end of the lamp, each socket being provided with a recess in a face extending to an edge thereof and spaced contact members in said recess, switch mechanism separate from said contact members carried by one of said sockets, said switch mechanism being controlled by movement of the lamp in said one socket and a source of potential including a resonant circuit connected to said contact members for energizing said cathodes, said resonant circuit including sai'd switch mechanism, said resonant circuit being broken by opening of said switch mechanism upon movement of the lamp in said one socket.

5. In combination with a double-ended discharge lamp having a cathode at each end connected to spaced contact prongs, a socket at each end of the lamp, each socket being provided with spaced contact members for engaging the lamp contact prongs, one of said sockets being provided with a switch mechanism separate from said contact members and controlled by movement of the lamp in said one socket, a 7

source of potential, a resonant circuit comprising a transformer and a capacitor connected in series with said switch mechanism and said source of potential, the secondaries of said transformer being electrically connected to the contact members each of said sockets for energizing the cathodes, said resonant circuit being broken upon opening of said switch mechanism upon movement of the lamp in said one socket.

6. In combination with a discharge lamp having a ferrule with two prongs, a combined switch and socket for connecting the lamp to a source of supply and for simultaneously closing a resonant circuit, said switch and socket having a back part with a recess, two contact members positioned in the recess and a front part with another recess and two contacts positioned in the last mentioned recess for cooperation with and switch member are moved during assembly and dismantling, the width of the slot being smaller than the spacing of the prongs to require turning movement of the lamp about its axis prior to removal of the lamp from the socket.

7. A socket comprising a rear casing half with a recess and two spaced contact members mounted therein, a front casing half having a recess with two other contact members mounted therein, each recess being extended through the respective casing half to form slots of different widths smaller than the spacing of the respective contact members.

8. A socket comprising a housing having front and back portions, and two pairs of contacts mounted in the front and back portions respectively with the contacts of each pair symmetrically spaced from a central plane through the housing, the spacing of the contacts in the back portion being greater than that of the contacts in the front portion, the front and top of the housing forming an opening having its largest dimension across the top of the back portion, the dimensions of the opening in the planes of the two pairs of contacts being smaller than the spacing of the respective pairs of contacts.

9, A socket for a discharge lamp having a ferrule with spaced contact prongs and a switch for closing a resonant circuit for such lamp, said socket comprising a housing, two pairs of spaced contacts held in the housing for cooperation with such prongs and switch respectively, one pair of contacts being located back of the other pair and spaced more than the latter, the front and top of the housing forming a slot of a shape and width requiring lateral insertion of the prongs and switch with the prongs in alignment and requiring subsequent to such insertion rotational movement of such lamp to effect engagement of the prongs and the switch with the respective contacts.

10. A socket for a discharge lamp having a ferrule with spaced contact prongs and a switch, said socket comprising a housing having a front portion with two spaced contacts mounted therein and a back portion with two other contacts mounted therein for cooperation with such switch and spaced more than the contacts in the front portion, the top and front of the housing forming an opening through which such prongs and switch may be inserted only laterally when in alignment, the slot in the front and back portions of the housing being narrower than the spacing of the respective contacts therein to require rotational movement of such lamp subsequent as insertion of the prongs and switch through the opening and prior to removal through the slot.

JOHN BERTRAM. 

